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Striatal opioid receptor availability is related to acute and chronic pain perception in arthritis: does opioid adaptation increase resilience to chronic pain? Pain 2016; 156:2267-2275. [PMID: 26176892 DOI: 10.1097/j.pain.0000000000000299] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The experience of pain in humans is modulated by endogenous opioids, but it is largely unknown how the opioid system adapts to chronic pain states. Animal models of chronic pain point to upregulation of opioid receptors (OpR) in the brain, with unknown functional significance. We sought evidence for a similar relationship between chronic pain and OpR availability in humans. Using positron emission tomography and the radiotracer (11)C-diprenorphine, patients with arthritis pain (n = 17) and healthy controls (n = 9) underwent whole-brain positron emission tomography scanning to calculate parametric maps of OpR availability. Consistent with the upregulation hypothesis, within the arthritis group, greater OpR availability was found in the striatum (including the caudate) of patients reporting higher levels of recent chronic pain, as well as regions of interest in the descending opioidergic pathway including the anterior cingulate cortex, thalamus, and periaqueductal gray. The functional significance of striatal changes were clarified with respect to acute pain thresholds: data across patients and controls revealed that striatal OpR availability was related to reduced pain perception. These findings are consistent with the view that chronic pain may upregulate OpR availability to dampen pain. Finally, patients with arthritis pain, compared with healthy controls, had overall less OpR availability within the striatum specifically, consistent with the greater endogenous opioid binding that would be expected in chronic pain states. Our observational evidence points to the need for further studies to establish the causal relationship between chronic pain states and OpR adaptation.
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52
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Vicente-Sanchez A, Segura L, Pradhan AA. The delta opioid receptor tool box. Neuroscience 2016; 338:145-159. [PMID: 27349452 DOI: 10.1016/j.neuroscience.2016.06.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/29/2016] [Accepted: 06/16/2016] [Indexed: 12/14/2022]
Abstract
In recent years, the delta opioid receptor has attracted increasing interest as a target for the treatment of chronic pain and emotional disorders. Due to their therapeutic potential, numerous tools have been developed to study the delta opioid receptor from both a molecular and a functional perspective. This review summarizes the most commonly available tools, with an emphasis on their use and limitations. Here, we describe (1) the cell-based assays used to study the delta opioid receptor. (2) The features of several delta opioid receptor ligands, including peptide and non-peptide drugs. (3) The existing approaches to detect delta opioid receptors in fixed tissue, and debates that surround these techniques. (4) Behavioral assays used to study the in vivo effects of delta opioid receptor agonists; including locomotor stimulation and convulsions that are induced by some ligands, but not others. (5) The characterization of genetically modified mice used specifically to study the delta opioid receptor. Overall, this review aims to provide a guideline for the use of these tools with the final goal of increasing our understanding of delta opioid receptor physiology.
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Affiliation(s)
| | - Laura Segura
- Department of Psychiatry, University of Illinois at Chicago, United States
| | - Amynah A Pradhan
- Department of Psychiatry, University of Illinois at Chicago, United States.
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53
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Peppin JF, Raffa RB. Delta opioid agonists: a concise update on potential therapeutic applications. J Clin Pharm Ther 2015; 40:155-66. [PMID: 25726896 DOI: 10.1111/jcpt.12244] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 12/24/2014] [Indexed: 01/23/2023]
Abstract
WHAT IS KNOWN AND OBJECTIVE The endogenous opioid system co-evolved with chemical defences, or at times symbiotic relationships, between plants and other autotrophs and heterotrophic predators - thus, it is not surprising that endogenous opioid ligands and exogenous mimetic ligands produce diverse physiological effects. Among the endogenous opioid peptides (endomorphins, enkephalins, dynorphins and nociception/orphanin FQ) derived from the precursors encoded by four genes (PNOC, PENK, PDYN and POMC) are the pentapeptides Met-enkephalin (Tyr-Gly-Gly-Phe-Met) and Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu). The physiological effects of the enkephalins are mediated via 7-transmembrane G protein-coupled receptors, including delta opioid receptor (DOR). We present a concise update on the status of progress and opportunities of this approach. METHODS A literature search of the PUBMED database and a combination of keywords including delta opioid receptor, analgesia, mood and individual compounds identified therein, from industry and other source, and from www.clinicaltrials.com. RESULTS AND DISCUSSION DOR agonist and antagonist ligands have been developed with ever increasing affinity and selectivity for DOR over other opioid receptor subtypes and studied for therapeutic utility, primarily for pain relief, but also for other clinical endpoints. WHAT IS NEW AND CONCLUSION Selective DOR agonists have been designed with a large increase in therapeutic window for a variety of potential CNS applications including pain, depression, and learning and memory among others.
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Affiliation(s)
- J F Peppin
- Center for Bioethics, Pain Management and Medicine, University City, MO, USA; Mallinckrodt Pharmaceuticals, Hazelwood, MO, USA
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54
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Dual allosteric modulation of opioid antinociceptive potency by α2A-adrenoceptors. Neuropharmacology 2015; 99:285-300. [PMID: 26254859 DOI: 10.1016/j.neuropharm.2015.08.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Revised: 07/09/2015] [Accepted: 08/04/2015] [Indexed: 12/31/2022]
Abstract
Opioid and α2-adrenoceptor (AR) agonists are analgesic when administered in the spinal cord and show a clinically beneficial synergistic interaction when co-administered. However, α2-AR antagonists can also inhibit opioid antinociception, suggesting a complex interaction between the two systems. The α2A-AR subtype is necessary for spinal adrenergic analgesia and synergy with opioids for most agonist combinations. Therefore, we investigated whether spinal opioid antinociception and opioid-adrenergic synergy were under allosteric control of the α2A-AR. Drugs were administered intrathecally in wild type (WT) and α2A-knock-out (KO) mice and antinociception was measured using the hot water tail immersion or substance P behavioral assays. The α2A-AR agonist clonidine was less effective in α2A-KO mice in both assays. The absence of the α2A-AR resulted in 10-70-fold increases in the antinociceptive potency of the opioid agonists morphine and DeltII. In contrast, neither morphine nor DeltII synergized with clonidine in α2A-KO mice, indicating that the α2AAR has both positive and negative modulatory effects on opioid antinociception. Depletion of descending adrenergic terminals with 6-OHDA resulted in a significant decrease in morphine efficacy in WT but not in α2A-KO mice, suggesting that endogenous norepinephrine acts through the α2A-AR to facilitate morphine antinociception. Based on these findings, we propose a model whereby ligand-occupied versus ligand-free α2A-AR produce distinct patterns of modulation of opioid receptor activation. In this model, agonist-occupied α2A-ARs potentiate opioid analgesia, while non-occupied α2A-ARs inhibit opioid analgesia. Exploiting such interactions between the two receptors could lead to the development of better pharmacological treatments for pain management.
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Pradhan AA, Tawfik VL, Tipton AF, Scherrer G. In vivo techniques to investigate the internalization profile of opioid receptors. Methods Mol Biol 2015; 1230:87-104. [PMID: 25293318 DOI: 10.1007/978-1-4939-1708-2_7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
G-protein-coupled receptors (GPCRs) regulate a remarkable diversity of biological functions, and are thus often targeted for drug therapies. Receptor internalization is commonly observed following agonist binding and activation. Receptor trafficking events have been well characterized in cell systems, but the in vivo significance of GPCR internalization is still poorly understood. To address this issue, we have developed an innovative knock-in mouse model, where an opioid receptor is directly visible in vivo. These knockin mice express functional fluorescent delta opioid receptors (DOR-eGFP) in place of the endogenous receptor, and these receptors are expressed at physiological levels within their native environment. DOR-eGFP mice have proven to be an extraordinary tool in studying receptor neuroanatomy, real-time receptor trafficking in live neurons, and in vivo receptor internalization. We have used this animal model to determine the relationship between receptor trafficking in neurons and receptor function at a behavioral level. Here, we describe in detail the construction and characterization of this knockin mouse. We also outline how to use these mice to examine the behavioral consequences of agonist-specific trafficking at the delta opioid receptor. These techniques are potentially applicable to any GPCR, and highlight the powerful nature of this imaging tool.
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Affiliation(s)
- Amynah A Pradhan
- Department of Psychiatry, University of Illinois at Chicago, 1601 W Taylor Street, Chicago, IL, 60612, USA,
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Brederson JD, Honda CN. Primary afferent neurons express functional delta opioid receptors in inflamed skin. Brain Res 2015; 1614:105-11. [PMID: 25911583 DOI: 10.1016/j.brainres.2015.04.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 04/01/2015] [Accepted: 04/13/2015] [Indexed: 11/16/2022]
Abstract
Peripherally-restricted opiate compounds attenuate hyperalgesia in experimental models of inflammatory pain, but have little discernable effect on nociceptive behavior in normal animals. This suggests that activation of opioid receptors on peripheral sensory axons contributes to decreased afferent activity after injury. Previously, we reported that direct application of morphine to cutaneous receptive fields decreased mechanical and heat-evoked responses in a population of C-fiber nociceptors in inflamed skin. Consistent with reported behavioral studies, direct application of morphine had no effect on fiber activity in control skin. The aim of the present study was to determine whether mechanical responsiveness of nociceptors innervating inflamed skin was attenuated by direct activation of delta opioid receptors (DORs) on peripheral terminals. An ex vivo preparation of rat plantar skin and tibial nerve was used to examine effects of a selective DOR agonist, deltorphin II, on responsiveness of single fibers innervating inflamed skin. Electrical recordings were made eighteen hours after injection of complete Freund's adjuvant into the hindpaw. Deltorphin II produced an inhibition of the mechanical responsiveness of single fibers innervating inflamed skin; an effect blocked by the DOR-selective antagonist, naltrindole. The population of units responsive to deltorphin II was identified as consisting of C fiber mechanical nociceptors.
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Affiliation(s)
| | - Christopher N Honda
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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Beaudry H, Mercier-Blais AA, Delaygue C, Lavoie C, Parent JL, Neugebauer W, Gendron L. Regulation of μ and δ opioid receptor functions: involvement of cyclin-dependent kinase 5. Br J Pharmacol 2015; 172:2573-87. [PMID: 25598508 PMCID: PMC4409908 DOI: 10.1111/bph.13088] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 12/18/2014] [Accepted: 01/05/2015] [Indexed: 12/26/2022] Open
Abstract
Background and Purpose Phosphorylation of δ opioid receptors (DOP receptors) by cyclin-dependent kinase 5 (CDK5) was shown to regulate the trafficking of this receptor. Therefore, we aimed to determine the role of CDK5 in regulating DOP receptors in rats treated with morphine or with complete Freund's adjuvant (CFA). As μ (MOP) and DOP receptors are known to be co-regulated, we also sought to determine if CDK5-mediated regulation of DOP receptors also affects MOP receptor functions. Experimental Approach The role of CDK5 in regulating opioid receptors in CFA- and morphine-treated rats was studied using roscovitine as a CDK inhibitor and a cell-penetrant peptide mimicking the second intracellular loop of DOP receptors (C11-DOPri2). Opioid receptor functions were assessed in vivo in a series of behavioural experiments and correlated by measuring ERK1/2 activity in dorsal root ganglia homogenates. Key Results Chronic roscovitine treatment reduced the antinociceptive and antihyperalgesic effects of deltorphin II (Dlt II) in morphine- and CFA-treated rats respectively. Repeated administrations of C11-DOPri2 also robustly decreased Dlt II-induced analgesia. Interestingly, DAMGO-induced analgesia was significantly increased by roscovitine and C11-DOPri2. Concomitantly, in roscovitine-treated rats the Dlt II-induced ERK1/2 activation was decreased, whereas the DAMGO-induced ERK1/2 activation was increased. An acute roscovitine treatment had no effect on Dlt II- or DAMGO-induced analgesia. Conclusions and Implications Together, our results demonstrate that CDK5 is a key player in the regulation of DOP receptors in morphine- and CFA-treated rats and that the regulation of DOP receptors by CDK5 is sufficient to modulate MOP receptor functions through an indirect process.
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Affiliation(s)
- H Beaudry
- Département de Physiologie et Biophysique, Université de Sherbrooke, Sherbrooke, QC, Canada; Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, QC, Canada; Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
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58
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Liu H, Wu QF, Li JY, Liu XJ, Li KC, Zhong YQ, Wu D, Wang Q, Lu YJ, Bao L, Zhang X. Fibroblast growth factor 7 is a nociceptive modulator secreted via large dense-core vesicles. J Mol Cell Biol 2015; 7:466-75. [PMID: 25782913 DOI: 10.1093/jmcb/mjv019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 02/02/2015] [Indexed: 11/13/2022] Open
Abstract
Fibroblast growth factor (FGF) 7, a member of FGF family, is initially found to be secreted from mesenchymal cells to repair epithelial tissues. However, its functions in the nervous system are largely unknown. The present study showed that FGF7 was a neuromodulator localized in the large dense-core vesicles (LDCVs) in nociceptive neurons. FGF7 was mainly expressed in small-diameter neurons of the dorsal root ganglion and could be transported to the dorsal spinal cord. Interestingly, FGF7 was mostly stored in LDCVs that did not contain neuropeptide substance P. Electrophysiological recordings in the spinal cord slice showed that buffer-applied FGF7 increased the amplitude of excitatory post-synaptic current evoked by stimulating the sensory afferent fibers. Behavior tests showed that intrathecally applied FGF7 potentiated the formalin-induced acute nociceptive response. Moreover, both acute and inflammatory nociceptive responses were significantly reduced in Fgf7-deficient mice. These results suggest that FGF7 exerts an excitatory modulation of nociceptive afferent transmission.
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Affiliation(s)
- Hui Liu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Qing-Feng Wu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jia-Yin Li
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xing-Jun Liu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Kai-Cheng Li
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yan-Qing Zhong
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Dan Wu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Qiong Wang
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yin-Jing Lu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Lan Bao
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Xu Zhang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
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Beaudry H, Gendron L, Morón JA. Implication of delta opioid receptor subtype 2 but not delta opioid receptor subtype 1 in the development of morphine analgesic tolerance in a rat model of chronic inflammatory pain. Eur J Neurosci 2015; 41:901--7. [PMID: 25639561 DOI: 10.1111/ejn.12829] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 11/11/2014] [Accepted: 12/10/2014] [Indexed: 12/20/2022]
Abstract
Opioids are well known for their robust analgesic effects. Chronic activation of mu opioid receptors (MOPs) is, however, accompanied by various unwanted effects such as analgesic tolerance. Among other mechanisms, interactions between MOPs and delta opioid receptors (DOPs) are thought to play an important role in morphine-induced behavioral adaptations. Interestingly, certain conditions such as inflammation enhance the function of the DOP through a MOP-dependent mechanism. Here, we investigated the role of DOPs during the development of morphine tolerance in an animal model of chronic inflammatory pain. Using behavioral approaches, we first established that repeated systemic morphine treatment induced morphine analgesic tolerance in rats coping with chronic inflammatory pain. We then observed that blockade of DOPs with subcutaneous naltrindole (NTI), a selective DOP antagonist, significantly attenuated the development of morphine tolerance in a dose-dependent manner. We confirmed that this effect was DOP mediated by showing that an acute injection of NTI had no effect on morphine-induced analgesia in naive animals. Previous pharmacological characterizations revealed the existence of DOP subtype 1 and DOP subtype 2. As opposed to NTI, 7-benzylidenenaltrexone and naltriben were reported to be selective DOP subtype 1 and DOP subtype 2 antagonists, respectively. Interestingly, naltriben but not 7-benzylidenenaltrexone was able to attenuate the development of morphine analgesic tolerance in inflamed rats. Altogether, our results suggest that targeting of DOP subtype 2 with antagonists provides a valuable strategy to attenuate the analgesic tolerance that develops after repeated morphine administration in the setting of chronic inflammatory pain.
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Affiliation(s)
- H Beaudry
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University Medical Center, Columbia University, P&S Box 46, 630 West 168th Street, New York, NY, 10032, USA; Department of Physiology and Biophysics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, QC, J1H 5N4, Canada
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Pradhan AA, Smith ML, Zyuzin J, Charles A. δ-Opioid receptor agonists inhibit migraine-related hyperalgesia, aversive state and cortical spreading depression in mice. Br J Pharmacol 2014; 171:2375-84. [PMID: 24467301 DOI: 10.1111/bph.12591] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 12/10/2013] [Accepted: 01/10/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Migraine is an extraordinarily common brain disorder for which treatment options continue to be limited. Agonists that activate the δ-opioid receptor may be promising for the treatment of migraine as they are highly effective for the treatment of chronic rather than acute pain, do not induce hyperalgesia, have low abuse potential and have anxiolytic and antidepressant properties. The aim of this study was to investigate the therapeutic potential of δ-opioid receptor agonists for migraine by characterizing their effects in mouse migraine models. EXPERIMENTAL APPROACH Mechanical hypersensitivity was assessed in mice treated with acute and chronic doses of nitroglycerin (NTG), a known human migraine trigger. Conditioned place aversion to NTG was also measured as a model of migraine-associated negative affect. In addition, we assessed evoked cortical spreading depression (CSD), an established model of migraine aura, in a thinned skull preparation. KEY RESULTS NTG evoked acute and chronic mechanical and thermal hyperalgesia in mice, as well as conditioned place aversion. Three different δ-opioid receptor agonists, SNC80, ARM390 and JNJ20788560, significantly reduced NTG-evoked hyperalgesia. SNC80 also abolished NTG-induced conditioned place aversion, suggesting that δ-opioid receptor activation may also alleviate the negative emotional state associated with migraine. We also found that SNC80 significantly attenuated CSD, a model that is considered predictive of migraine preventive therapies. CONCLUSIONS AND IMPLICATIONS These data show that δ-opioid receptor agonists modulate multiple basic mechanisms associated with migraine, indicating that δ-opioid receptors are a promising therapeutic target for this disorder.
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Affiliation(s)
- Amynah A Pradhan
- Semel Institute for Neuropsychiatry & Human Behavior, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Headache Research and Treatment Program, Department of Neurology David Geffen School of Medicine, UCLA, Los Angeles, CA, USA; Shirley and Stefan Hatos Center for Neuropharmacology, UCLA, Los Angeles, CA, USA; Department of Psychiatry, University of Illinois at Chicago (UIC), Chicago, IL, USA
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Aira Z, Barrenetxea T, Buesa I, Azkue JJ. Plasticity of α2-adrenergic spinal antinociception following nerve injury: selective, bidirectional interaction with the delta opioid receptor. Brain Res 2014; 1594:190-203. [PMID: 25446445 DOI: 10.1016/j.brainres.2014.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 11/04/2014] [Accepted: 11/06/2014] [Indexed: 11/25/2022]
Abstract
Interactions of opioid receptors with other receptor families can be made use of to improve analgesia and reduce adverse effects of opioid analgesics. We investigated interactions of the α2-adrenergic receptor (α2AR) with opioid receptors of the mu (MOR) and delta (DOR) types in the spinal dorsal horn in an animal model of neuropathic pain induced by spinal nerve ligation. Nine days after nerve injury, immunoreactivity for the α2AR subtype A (α2AAR) was increased both in tissue homogenates and at pre- and post-synaptic sites in transverse sections. The efficacy of spinally administered α2AAR agonist guanfacine at reducing C-fiber-evoked field potentials was increased in nerve-ligated rats. This reducing effect was impaired by simultaneous administration of DOR antagonist naltrindole, but not MOR antagonist CTOP, suggesting that concurrent DOR activation was required for α2AAR-mediated inhibition. While DOR agonist deltorphin II and MOR agonist DAMGO both effectively depressed C-fiber-evoked spinal field potentials, DOR- but not MOR-mediated depression was enhanced by subclinical guanfacine. In conscious, nerve-ligated rats, chronically administered deltorphin II produced stable thermal and mechanical antinociception over the 9 following days after nerve injury without apparent signs of habituation. Such an effect was dramatically enhanced by co-administration of a low dose of guanfacine, which reversed thermal and mechanical thresholds to levels near those prior to injury. The results suggest that spinal, α2AAR-mediated antinociception is increased after nerve injury and based on DOR co-activation. We demonstrate in vivo that α2AAR/DOR interaction can be exploited to provide effective behavioral antinociception during neuropathic pain.
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Affiliation(s)
- Zigor Aira
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Teresa Barrenetxea
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Itsaso Buesa
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain
| | - Jon Jatsu Azkue
- Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, PO Box 699, 48080 Bilbao, Spain.
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Abstract
Painful sensation is a hallmark of microbe-induced inflammation. This inflammatory pain is downregulated a few days after infection by opioids locally released by effector T lymphocytes generated in response to microbe-derived antigens. This review focuses on the endogenous regulation of inflammatory pain associated with adaptive T-cell response and puts in perspective the clinical consequences of the opioid-mediated analgesic activity of colitogenic T lymphocytes in inflammatory bowel disease.
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63
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Mika J, Popiolek-Barczyk K, Rojewska E, Makuch W, Starowicz K, Przewlocka B. Delta-opioid receptor analgesia is independent of microglial activation in a rat model of neuropathic pain. PLoS One 2014; 9:e104420. [PMID: 25105291 PMCID: PMC4126741 DOI: 10.1371/journal.pone.0104420] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 07/09/2014] [Indexed: 12/15/2022] Open
Abstract
The analgesic effect of delta-opioid receptor (DOR) ligands in neuropathic pain is not diminished in contrast to other opioid receptor ligands, which lose their effectiveness as analgesics. In this study, we examine whether this effect is related to nerve injury-induced microglial activation. We therefore investigated the influence of minocycline-induced inhibition of microglial activation on the analgesic effects of opioid receptor agonists: morphine, DAMGO, U50,488H, DPDPE, Deltorphin II and SNC80 after chronic constriction injury (CCI) to the sciatic nerve in rats. Pre-emptive and repeated administration of minocycline (30 mg/kg, i.p.) over 7 days significantly reduced allodynia and hyperalgesia as measured on day 7 after CCI. The antiallodynic and antihyperalgesic effects of intrathecally (i.t.) administered morphine (10–20 µg), DAMGO (1–2 µg) and U50,488H (25–50 µg) were significantly potentiated in rats after minocycline, but no such changes were observed after DPDPE (10–20 µg), deltorphin II (1.5–15 µg) and SNC80 (10–20 µg) administration. Additionally, nerve injury-induced down-regulation of all types of opioid receptors in the spinal cord and dorsal root ganglia was not influenced by minocycline, which indicates that the effects of opioid ligands are dependent on other changes, presumably neuroimmune interactions. Our study of rat primary microglial cell culture using qRT-PCR, Western blotting and immunocytochemistry confirmed the presence of mu-opioid receptors (MOR) and kappa-opioid receptors (KOR), further we provide the first evidence for the lack of DOR on microglial cells. In summary, DOR analgesia is different from analgesia induced by MOR and KOR receptors because it does not dependent on injury-induced microglial activation. DOR agonists appear to be the best candidates for new drugs to treat neuropathic pain.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/administration & dosage
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/therapeutic use
- Analgesics, Opioid/administration & dosage
- Analgesics, Opioid/therapeutic use
- Animals
- Anti-Bacterial Agents/administration & dosage
- Anti-Bacterial Agents/therapeutic use
- Cells, Cultured
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/administration & dosage
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/therapeutic use
- Gene Expression Regulation/drug effects
- Male
- Microglia/cytology
- Microglia/drug effects
- Microglia/metabolism
- Minocycline/administration & dosage
- Minocycline/therapeutic use
- Morphine/administration & dosage
- Morphine/therapeutic use
- Neuralgia/drug therapy
- Rats, Wistar
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
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Affiliation(s)
- Joanna Mika
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
- * E-mail: (BP); (JM)
| | | | - Ewelina Rojewska
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Wioletta Makuch
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Katarzyna Starowicz
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Barbara Przewlocka
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
- * E-mail: (BP); (JM)
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Chabot-Doré AJ, Schuster DJ, Stone LS, Wilcox GL. Analgesic synergy between opioid and α2 -adrenoceptors. Br J Pharmacol 2014; 172:388-402. [PMID: 24641506 DOI: 10.1111/bph.12695] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 03/08/2014] [Accepted: 03/12/2014] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED Opioid and α2 -adrenoceptor agonists are potent analgesic drugs and their analgesic effects can synergize when co-administered. These supra-additive interactions are potentially beneficial clinically; by increasing efficacy and/or reducing the total drug required to produce sufficient pain relief, undesired side effects can be minimized. However, combination therapies of opioids and α2 -adrenoceptor agonists remain underutilized clinically, in spite of a large body of preclinical evidence describing their synergistic interaction. One possible obstacle to the translation of preclinical findings to clinical applications is a lack of understanding of the mechanisms underlying the synergistic interactions between these two drug classes. In this review, we provide a detailed overview of the interactions between different opioid and α2 -adrenoceptor agonist combinations in preclinical studies. These studies have identified the spinal cord as an important site of action of synergistic interactions, provided insights into which receptors mediate these interactions and explored downstream signalling events enabling synergy. It is now well documented that the activation of both μ and δ opioid receptors can produce synergy with α2 -adrenoceptor agonists and that α2 -adrenoceptor agonists can mediate synergy through either the α2A or the α2C adrenoceptor subtypes. Current hypotheses surrounding the cellular mechanisms mediating opioid-adrenoceptor synergy, including PKC signalling and receptor oligomerization, and the evidence supporting them are presented. Finally, the implications of these findings for clinical applications and drug discovery are discussed. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- A-J Chabot-Doré
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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Gendron L, Mittal N, Beaudry H, Walwyn W. Recent advances on the δ opioid receptor: from trafficking to function. Br J Pharmacol 2014; 172:403-19. [PMID: 24665909 DOI: 10.1111/bph.12706] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/17/2014] [Accepted: 03/18/2014] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED Within the opioid family of receptors, δ (DOPrs) and μ opioid receptors (MOPrs) are typical GPCRs that activate canonical second-messenger signalling cascades to influence diverse cellular functions in neuronal and non-neuronal cell types. These receptors activate well-known pathways to influence ion channel function and pathways such as the map kinase cascade, AC and PI3K. In addition new information regarding opioid receptor-interacting proteins, downstream signalling pathways and resultant functional effects has recently come to light. In this review, we will examine these novel findings focusing on the DOPr and, in doing so, will contrast and compare DOPrs with MOPrs in terms of differences and similarities in function, signalling pathways, distribution and interactions. We will also discuss and clarify issues that have recently surfaced regarding the expression and function of DOPrs in different cell types and analgesia. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Louis Gendron
- Département de physiologie et biophysique, Institut de pharmacologie de Sherbrooke, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
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Ligand- and cell-dependent determinants of internalization and cAMP modulation by delta opioid receptor (DOR) agonists. Cell Mol Life Sci 2014; 71:1529-46. [PMID: 24022593 DOI: 10.1007/s00018-013-1461-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 08/13/2013] [Accepted: 08/19/2013] [Indexed: 10/26/2022]
Abstract
Signaling bias refers to G protein-coupled receptor ligand ability to preferentially activate one type of signal over another. Bias to evoke signaling as opposed to sequestration has been proposed as a predictor of opioid ligand potential for generating tolerance. Here we measured whether delta opioid receptor agonists preferentially inhibited cyclase activity over internalization in HEK cells. Efficacy (τ) and affinity (KA) values were estimated from functional data and bias was calculated from efficiency coefficients (log τ/KA). This approach better represented the data as compared to alternative methods that estimate bias exclusively from τ values. Log (τ/KA) coefficients indicated that SNC-80 and UFP-512 promoted cyclase inhibition more efficiently than DOR internalization as compared to DPDPE (bias factor for SNC-80: 50 and for UFP-512: 132). Molecular determinants of internalization were different in HEK293 cells and neurons with βarrs contributing to internalization in both cell types, while PKC and GRK2 activities were only involved in neurons. Rank orders of ligand ability to engage different internalization mechanisms in neurons were compared to rank order of E max values for cyclase assays in HEK cells. Comparison revealed a significant reversal in rank order for cyclase E max values and βarr-dependent internalization in neurons, indicating that these responses were ligand-specific. Despite this evidence, and because kinases involved in internalization were not the same across cellular backgrounds, it is not possible to assert if the magnitude and nature of bias revealed by rank orders of maximal responses is the same as the one measured in HEK cells.
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67
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Sukhtankar DD, Lee H, Rice KC, Ko MC. Differential effects of opioid-related ligands and NSAIDs in nonhuman primate models of acute and inflammatory pain. Psychopharmacology (Berl) 2014; 231:1377-87. [PMID: 24217900 PMCID: PMC3954905 DOI: 10.1007/s00213-013-3341-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 10/09/2013] [Indexed: 11/30/2022]
Abstract
RATIONALE Carrageenan-induced hyperalgesia is a widely used pain model in rodents. However, characteristics of carrageenan-induced hyperalgesia and effects of analgesic drugs under these conditions are unknown in nonhuman primates. OBJECTIVE The aims of this study were to develop carrageenan-induced hyperalgesia in rhesus monkeys and determine the efficacy and potency of agonists selective for the four opioid receptor subtypes in this model versus acute pain, as compared to non-steroidal anti-inflammatory drugs (NSAIDs). RESULTS Tail injection of carrageenan produced long-lasting thermal hyperalgesia in monkeys. Systemically administered agonists selective for opioid receptor subtypes, i.e., fentanyl (mu/MOP), U-50488H (kappa/KOP), SNC80 (delta/DOP) and Ro 64-6198 (nociceptin/orphanin FQ/NOP) dose-dependently attenuated carrageenan-induced thermal hyperalgesia with different potencies. In absence of carrageenan, these agonists, except SNC80, blocked acute thermal nociception. Opioid-related ligands, especially Ro 64-6198, were much more potent for their antihyperalgesic than antinociceptive effects. Both effects were mediated by the corresponding receptor mechanisms. Only fentanyl produced scratching at antihyperalgesic and antinociceptive doses consistent with its pruritic effects in humans, illustrating a translational profile of MOP agonists in nonhuman primates. Similar to SNC80, systemically administered NSAIDs ketorolac and naproxen dose-dependently attenuated carrageenan-induced hyperalgesia but not acute nociception. CONCLUSION Using two different pain modalities in nonhuman primates, effectiveness of clinically available analgesics like fentanyl, ketorolac and naproxen was distinguished and their efficacies and potencies were compared with the selective KOP, DOP, and NOP agonists. The opioid-related ligands displayed differential pharmacological properties in regulating hyperalgesia and acute nociception in the same subjects. Such preclinical primate models can be used to investigate novel analgesic agents.
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Affiliation(s)
- Devki D. Sukhtankar
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA,Corresponding authors: Dr. D. Sukhtankar () and Dr. H. Lee ()
| | - Heeseung Lee
- Department of Anesthesiology and Pain Medicine, School of Medicine, Ewha Womans University, Seoul 158-710, S. Korea,Corresponding authors: Dr. D. Sukhtankar () and Dr. H. Lee ()
| | - Kenner C. Rice
- Chemical Biology Research Branch, National Institute on Drug Abuse, Bethesda, MD 20892, USA
| | - Mei-Chuan Ko
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA,Center for Comparative Medicine Research, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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68
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Zambelli VO, Fernandes ACDO, Gutierrez VP, Ferreira JCB, Parada CA, Mochly-Rosen D, Cury Y. Peripheral sensitization increases opioid receptor expression and activation by crotalphine in rats. PLoS One 2014; 9:e90576. [PMID: 24594607 PMCID: PMC3942445 DOI: 10.1371/journal.pone.0090576] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 02/04/2014] [Indexed: 11/19/2022] Open
Abstract
Inflammation enhances the peripheral analgesic efficacy of opioid drugs, but the mechanisms involved in this phenomenon have not been fully elucidated. Crotalphine (CRP), a peptide that was first isolated from South American rattlesnake C.d. terrificus venom, induces a potent and long-lasting anti-nociceptive effect that is mediated by the activation of peripheral opioid receptors. Because the high efficacy of CRP is only observed in the presence of inflammation, we aimed to elucidate the mechanisms involved in the CRP anti-nociceptive effect induced by inflammation. Using real-time RT-PCR, western blot analysis and ELISA assays, we demonstrate that the intraplantar injection of prostaglandin E2 (PGE2) increases the mRNA and protein levels of the µ- and κ-opioid receptors in the dorsal root ganglia (DRG) and paw tissue of rats within 3 h of the injection. Using conformation state-sensitive antibodies that recognize activated opioid receptors, we show that PGE2, alone does not increase the activation of these opioid receptors but that in the presence of PGE2, the activation of specific opioid receptors by CRP and selective µ- and κ-opioid receptor agonists (positive controls) increases. Furthermore, PGE2 down-regulated the expression and activation of the δ-opioid receptor. CRP increased the level of activated mitogen-activated protein kinases in cultured DRG neurons, and this increase was dependent on the activation of protein kinase Cζ. This CRP effect was much more prominent when the cells were pretreated with PGE2. These results indicate that the expression and activation of peripheral opioid receptors by opioid-like drugs can be up- or down-regulated in the presence of an acute injury and that acute tissue injury enhances the efficacy of peripheral opioids.
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MESH Headings
- Analgesics, Opioid/isolation & purification
- Analgesics, Opioid/pharmacology
- Analgesics, Opioid/therapeutic use
- Animals
- Crotalus/metabolism
- Dinoprostone
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/immunology
- Ganglia, Spinal/metabolism
- Gene Expression Regulation/drug effects
- Hyperalgesia/chemically induced
- Hyperalgesia/drug therapy
- Hyperalgesia/genetics
- Hyperalgesia/immunology
- Male
- Peptides/isolation & purification
- Peptides/pharmacology
- Peptides/therapeutic use
- Rats
- Rats, Wistar
- Receptors, Opioid/agonists
- Receptors, Opioid/genetics
- Receptors, Opioid/immunology
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Affiliation(s)
| | | | | | | | - Carlos Amilcar Parada
- Departamento de Fisiologia e Biofísica, Instituto de Biociências (UNICAMP) Rua Monteiro Lobato, Cidade Universitária, Campinas, SP, Brazil
| | - Daria Mochly-Rosen
- Department of Chemical and Systems Biology, Stanford University, School of Medicine, Stanford, California, United States of America
| | - Yara Cury
- Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil
- * E-mail:
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69
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Learning-related translocation of δ-opioid receptors on ventral striatal cholinergic interneurons mediates choice between goal-directed actions. J Neurosci 2013; 33:16060-71. [PMID: 24107940 DOI: 10.1523/jneurosci.1927-13.2013] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The ability of animals to extract predictive information from the environment to inform their future actions is a critical component of decision-making. This phenomenon is studied in the laboratory using the pavlovian-instrumental transfer protocol in which a stimulus predicting a specific pavlovian outcome biases choice toward those actions earning the predicted outcome. It is well established that this transfer effect is mediated by corticolimbic afferents on the nucleus accumbens shell (NAc-S), and recent evidence suggests that δ-opioid receptors (DORs) play an essential role in this effect. In DOR-eGFP knock-in mice, we show a persistent, learning-related plasticity in the translocation of DORs to the somatic plasma membrane of cholinergic interneurons (CINs) in the NAc-S during the encoding of the specific stimulus-outcome associations essential for pavlovian-instrumental transfer. We found that increased membrane DOR expression reflected both stimulus-based predictions of reward and the degree to which these stimuli biased choice during the pavlovian-instrumental transfer test. Furthermore, this plasticity altered the firing pattern of CINs increasing the variance of action potential activity, an effect that was exaggerated by DOR stimulation. The relationship between the induction of membrane DOR expression in CINs and both pavlovian conditioning and pavlovian-instrumental transfer provides a highly specific function for DOR-related modulation in the NAc-S, and it is consistent with an emerging role for striatal CIN activity in the processing of predictive information. Therefore, our results reveal evidence of a long-term, experience-dependent plasticity in opioid receptor expression on striatal modulatory interneurons critical for the cognitive control of action.
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70
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Largent-Milnes TM, Brookshire SW, Skinner DP, Hanlon KE, Giuvelis D, Yamamoto T, Davis P, Campos CR, Nair P, Deekonda S, Bilsky EJ, Porreca F, Hruby VJ, Vanderah TW. Building a better analgesic: multifunctional compounds that address injury-induced pathology to enhance analgesic efficacy while eliminating unwanted side effects. J Pharmacol Exp Ther 2013; 347:7-19. [PMID: 23860305 PMCID: PMC3781412 DOI: 10.1124/jpet.113.205245] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 07/08/2013] [Indexed: 12/27/2022] Open
Abstract
The most highly abused prescription drugs are opioids used for the treatment of pain. Physician-reported drug-seeking behavior has resulted in a significant health concern among doctors trying to adequately treat pain while limiting the misuse or diversion of pain medications. In addition to abuse liability, opioid use is associated with unwanted side effects that complicate pain management, including opioid-induced emesis and constipation. This has resulted in restricting long-term doses of opioids and inadequate treatment of both acute and chronic debilitating pain, demonstrating a compelling need for novel analgesics. Recent reports indicate that adaptations in endogenous substance P/neurokinin-1 receptor (NK1) are induced by chronic pain and sustained opioid exposure, and these changes may contribute to processes responsible for opioid abuse liability, emesis, and analgesic tolerance. Here, we describe a multifunctional mu-/delta-opioid agonist/NK1 antagonist compound [Tyr-d-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-Bn(CF3)2 (TY027)] that has a preclinical profile of excellent antinociceptive efficacy, low abuse liability, and no opioid-related emesis or constipation. In rodent models of acute and neuropathic pain, TY027 demonstrates analgesic efficacy following central or systemic administration with a plasma half-life of more than 4 hours and central nervous system penetration. These data demonstrate that an innovative opioid designed to contest the pathology created by chronic pain and sustained opioids results in antinociceptive efficacy in rodent models, with significantly fewer side effects than morphine. Such rationally designed, multitargeted compounds are a promising therapeutic approach in treating patients who suffer from acute and chronic pain.
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Affiliation(s)
- T M Largent-Milnes
- Department of Pharmacology (T.M.L.-M., S.W.B., D.P.S., K.E.H., P.D., C.R.C., F.P., T.W.V.), and Department of Chemistry (T.Y., P.N, S.D., V.J.H.), University of Arizona, Tucson, Arizona; and Center for Excellence in Neuroscience, University of New England, Biddeford, Maine (K.E.H., D.G., E.J.B., F.P., T.W.V.)
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71
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Leal AK, Yamauchi K, Kim J, Ruiz-Velasco V, Kaufman MP. Peripheral δ-opioid receptors attenuate the exercise pressor reflex. Am J Physiol Heart Circ Physiol 2013; 305:H1246-55. [PMID: 23934854 DOI: 10.1152/ajpheart.00116.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In rats with ligated femoral arteries, the exercise pressor reflex is exaggerated, an effect that is attenuated by stimulation of peripheral μ-opioid receptors on group IV metabosensitive afferents. In contrast, δ-opioid receptors are expressed mostly on group III mechanosensitive afferents, a finding that prompted us to determine whether stimulation of these opioid receptors could also attenuate the exaggerated exercise pressor reflex in "ligated" rats. We found femoral arterial injection of [D-Pen2,D-Pen5]enkephalin (DPDPE; 1.0 μg), a δ-opioid agonist, significantly attenuated the pressor and cardioaccelerator components of the exercise pressor reflex evoked by hindlimb muscle contraction in both rats with ligated and patent femoral arteries. DPDPE significantly decreased the pressor responses to muscle mechanoreflex activation, evoked by tendon stretch, in ligated rats only. DPDPE (1.0 μg) had no effect in either group on the pressor and cardioaccelerator responses to capsaicin (0.2 μg), which primarily stimulates group IV afferents. DPDPE (1.0 μg) had no effect on the pressor and cardioaccelerator responses to lactic acid (24 mM), which stimulates group III and IV afferents, in rats with patent femoral arteries but significantly decreased the pressor response in ligated rats. Western blots revealed the amount of protein comprising the δ-opioid receptor was greater in dorsal root ganglia innervating hindlimbs with ligated femoral arteries than in dorsal root ganglia innervating hindlimbs with patent femoral arteries. Our findings support the hypothesis that stimulation of δ-opioid receptors on group III afferents attenuated the exercise pressor reflex.
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Affiliation(s)
- Anna K Leal
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania; and
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72
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Normandin A, Luccarini P, Molat JL, Gendron L, Dallel R. Spinal μ and δ opioids inhibit both thermal and mechanical pain in rats. J Neurosci 2013; 33:11703-14. [PMID: 23843537 PMCID: PMC3855450 DOI: 10.1523/jneurosci.1631-13.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/04/2013] [Accepted: 06/07/2013] [Indexed: 11/21/2022] Open
Abstract
The expression and contribution of μ (MOPR) and δ opioid receptors (DOPR) in polymodal nociceptors have been recently challenged. Indeed, MOPR and DOPR were shown to be expressed in distinct subpopulation of nociceptors where they inhibit pain induced by noxious heat and mechanical stimuli, respectively. In the present study, we used electrophysiological measurements to assess the effect of spinal MOPR and DOPR activation on heat-induced and mechanically induced diffuse noxious inhibitory controls (DNICs). We recorded from wide dynamic range neurons in the spinal trigeminal nucleus of anesthetized rats. Trains of 105 electrical shocks were delivered to the excitatory cutaneous receptive field. DNICs were triggered either by immersion of the hindpaw in 49°C water or application of 300 g of mechanical pressure. To study the involvement of peptidergic primary afferents in the activation of DNIC by noxious heat and mechanical stimulations, substance P release was measured in the spinal cord by visualizing neurokinin type 1 receptor internalization. We found that the activation of spinal MOPR and DOPR similarly attenuates the DNIC and neurokinin type 1 receptor internalization induced either by heat or mechanical stimuli. Our results therefore reveal that the activation of spinal MOPR and DOPR relieves both heat-induced and mechanically induced pain with similar potency and suggest that these receptors are expressed on polymodal, substance P-expressing neurons.
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Affiliation(s)
- Audrey Normandin
- Département de physiologie et biophysique, Faculté de médecine et des sciences de la santé
| | - Philippe Luccarini
- Clermont Université, Université d'Auvergne, NEURO-DOL, BP 10448, F-63000, CLERMONT-FERRAND Inserm, U1107, F-63001 Clermont-Ferrand, France
| | - Jean-Louis Molat
- Clermont Université, Université d'Auvergne, NEURO-DOL, BP 10448, F-63000, CLERMONT-FERRAND Inserm, U1107, F-63001 Clermont-Ferrand, France
| | - Louis Gendron
- Département de physiologie et biophysique, Faculté de médecine et des sciences de la santé
- Institut de pharmacologie de Sherbrooke, and
- Centre de recherche clinique Étienne-Le Bel, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada, and
| | - Radhouane Dallel
- Clermont Université, Université d'Auvergne, NEURO-DOL, BP 10448, F-63000, CLERMONT-FERRAND Inserm, U1107, F-63001 Clermont-Ferrand, France
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73
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Pharmacological traits of delta opioid receptors: pitfalls or opportunities? Psychopharmacology (Berl) 2013; 228:1-18. [PMID: 23649885 PMCID: PMC3679311 DOI: 10.1007/s00213-013-3129-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 04/15/2013] [Indexed: 12/11/2022]
Abstract
RATIONALE Delta opioid receptors (DORs) have been considered as a potential target to relieve pain as well as treat depression and anxiety disorders and are known to modulate other physiological responses, including ethanol and food consumption. A small number of DOR-selective drugs are in clinical trials, but no DOR-selective drugs have been approved by the Federal Drug Administration and some candidates have failed in phase II clinical trials, highlighting current difficulties producing effective delta opioid-based therapies. Recent studies have provided new insights into the pharmacology of the DOR, which is often complex and at times paradoxical. OBJECTIVE This review will discuss the existing literature focusing on four aspects: (1) Two DOR subtypes have been postulated based on differences in pharmacological effects of existing DOR-selective ligands. (2) DORs are expressed ubiquitously throughout the body and central nervous system and are, thus, positioned to play a role in a multitude of diseases. (3) DOR expression is often dynamic, with many reports of increased expression during exposure to chronic stimuli, such as stress, inflammation, neuropathy, morphine, or changes in endogenous opioid tone. (4) A large structural variety in DOR ligands implies potential different mechanisms of activating the receptor. CONCLUSION The reviewed features of DOR pharmacology illustrate the potential benefit of designing tailored or biased DOR ligands.
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74
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Pettinger L, Gigout S, Linley JE, Gamper N. Bradykinin controls pool size of sensory neurons expressing functional δ-opioid receptors. J Neurosci 2013; 33:10762-71. [PMID: 23804098 PMCID: PMC3724994 DOI: 10.1523/jneurosci.0123-13.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 05/21/2013] [Accepted: 05/22/2013] [Indexed: 11/21/2022] Open
Abstract
Analgesics targeting the δ-opioid receptor (DOR) may lead to fewer side effects than conventional opioid drugs, which mainly act on μ-opioid receptors (MOR), because of the less abundant expression of DOR in the CNS compared with MOR. Analgesic potential of DOR agonists increases after inflammation, an effect that may be mediated by DOR expressed in the peripheral sensory fibers. However, the expression of functional DOR at the plasma membrane of sensory neurons is controversial. Here we have used patch-clamp recordings and total internal reflection fluorescence microscopy to study the functional expression of DOR in sensory neurons from rat trigeminal (TG) and dorsal root ganglia (DRG). Real-time total internal reflection fluorescence microscopy revealed that treatment of TG and DRG cultures with the inflammatory mediator bradykinin (BK) caused robust trafficking of heterologously expressed GFP-tagged DOR to the plasma membrane. By contrast, treatment of neurons with the DOR agonist [d-Ala(2), d-Leu(5)]-enkephalin (DADLE) caused a decrease in the membrane abundance of DOR, suggesting internalization of the receptor after agonist binding. Patch-clamp experiments revealed that DADLE inhibited voltage-gated Ca(2+) channels (VGCCs) in 23% of small-diameter TG neurons. Pretreatment with BK resulted in more than twice as many DADLE responsive neurons (54%) but did not affect the efficacy of VGCC inhibition by DADLE. Our data suggest that inflammatory mediator-induced membrane insertion of DOR into the plasma membrane of peripheral sensory neurons may underlie increased DOR analgesia in inflamed tissue. Furthermore, the majority of BK-responsive TG neurons may have a potential to become responsive to DOR ligands in inflammatory conditions.
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Affiliation(s)
- Louisa Pettinger
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Sylvain Gigout
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - John E. Linley
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Nikita Gamper
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
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75
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Pradhan AA, Smith ML, Kieffer BL, Evans CJ. Ligand-directed signalling within the opioid receptor family. Br J Pharmacol 2013; 167:960-9. [PMID: 22708627 DOI: 10.1111/j.1476-5381.2012.02075.x] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The classic model of GPCR activation proposed that all agonists induce the same active receptor conformation. However, research over the last decade has shown that GPCRs exist in multiple conformations, and that agonists can stabilize different active states. The distinct receptor conformations induced by ligands result in distinct receptor-effector complexes, which produce varying levels of activation or inhibition of subsequent signalling cascades. This concept, referred to as ligand-directed signalling or biased agonism has important biological and therapeutic implications. Opioid receptors are G(i/o) GPCRs and regulate a number of important physiological functions, including pain, reward, mood, stress, gastrointestinal transport and respiration. A number of in vitro studies have shown biased agonism at the three opioid receptors (µ, δ and κ); however, in vivo consequences of this phenomenon have only recently been demonstrated. For the µ and δ opioid receptors, the majority of reported ligand selective behavioural effects are observed as differential adaptations to repeated drug administration. In terms of the κ opioid receptor, clear links between ligand-selective signalling events and specific in vivo responses have been recently characterized. Drugs for all three receptors are either already used or are being developed for clinical applications. There is clearly a need to better characterize the specific events that occur following agonist stimulation and how these relate to in vivo responses. This understanding could eventually lead to the development of tailor-made pharmacotherapies where advantageous drug effects can be selectively targeted over adverse effects.
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Affiliation(s)
- Amynah A Pradhan
- Semel Institute for Neuropsychiatry & Human Behavior, University of California Los Angeles, Los Angeles, CA 90024-1759, USA.
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76
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Molet J, Pohl M. Gene-based approaches in pain research and exploration of new therapeutic targets and strategies. Eur J Pharmacol 2013; 716:129-41. [PMID: 23500201 DOI: 10.1016/j.ejphar.2013.01.073] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 01/17/2013] [Accepted: 01/29/2013] [Indexed: 12/18/2022]
Abstract
Large panel of gene-based techniques is used for many years specifically in the pain research field. From the first identification (cloning) of some "mythic" genes, such as those encoding opioid or capsaicin receptors allowing then the creation of first-generation knockout mice, to the today conditional (time, tissue, cell-type and even pathology-dependent) and regulatable modulation of a gene function, these approaches largely contributed to fundamental leaps forward in our understanding of the function of some proteins and of their interest as possible druggable targets. Perhaps one of the most remarkable evolution in the last years is the passage of these approaches from the bench to the patient; whether it concerns the identification of genes involved in inherited pain insensibility/susceptibility, the search for genetic markers of pain types, the individual pharmacogenomics or even the first gene therapy trials. From many possible variants of gene-grounded techniques used in pain research we focus here on gene knockouts and some recent developments, on viral vectors-based gene transfer and on transgenic models for the tracing of pain pathways. Through these selected examples we attempted to emphasize the immense potential of these approaches and their already well-recognized contribution in both the basic and clinical pain research.
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Affiliation(s)
- Jenny Molet
- INSERM UMRS 975, CNRS UMR 7225, UPMC, Equipe Douleurs , Faculté de Médecine Pitié-Salpêtrière, 91 Bd de l'Hôpital, 75013 Paris, France.
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77
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Pradhan A, Smith M, McGuire B, Evans C, Walwyn W. Chronic inflammatory injury results in increased coupling of delta opioid receptors to voltage-gated Ca2+ channels. Mol Pain 2013; 9:8. [PMID: 23497324 PMCID: PMC3621800 DOI: 10.1186/1744-8069-9-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 02/25/2013] [Indexed: 12/31/2022] Open
Abstract
Background Opioid receptors regulate a diverse array of physiological functions. Mu opioid receptor agonists are well-known analgesics for treating acute pain. In contrast, animal models suggest that chronic pain is more effectively relieved by delta opioid receptor agonists. A number of studies have shown that chronic pain results in increased function of delta opioid receptors. This is proposed to result from enhanced trafficking of the delta opioid receptor to the cell membrane induced by persistent tissue injury. However, recent studies have questioned this mechanism, which has resulted in some uncertainty as to whether delta opioid receptors are indeed upregulated in chronic pain states. To clarify this question, we have examined the effect of chronic inflammatory pain over time using both an ex vivo measure of delta function: receptor-Ca2+ channel coupling, and an in vivo measure; the relief of chronic pain by a delta opioid receptor agonist. In addition, as beta-arrestin 2 can regulate delta opioid receptor trafficking and signaling, we have further examined whether deleting this scaffolding and signal transduction molecule alters delta opioid receptor function. Results We used the Complete Freund’s Adjuvant model of inflammatory pain, and examined the effectiveness of the delta agonist, SNC80, to both inhibit Ca2+ channels in primary afferent neurons and to attenuate mechanical allodynia. In naïve beta-arrestin 2 wildtype and knockout mice, SNC80 neither significantly inhibited voltage-dependent Ca2+ currents nor produced antinociception. However, following inflammatory pain, both measures showed a significant and long-lasting enhancement of delta opioid receptor function that persisted for up to 14 days post-injury regardless of genotype. Furthermore, although this pain model did not alter Ca2+ current density, the contribution of N-type Ca2+ channels to the total current appeared to be regulated by the presence of beta-arrestin 2. Conclusions Our results indicate that there is an upregulation of delta opioid receptor function following chronic pain. This gain of function is reflected in the increased efficacy of a delta agonist in both behavioral and electrophysiological measures. Overall, this work confirms that delta opioid receptors can be enhanced following tissue injury associated with chronic pain.
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Affiliation(s)
- Amynah Pradhan
- Department of Neuropsychiatry and Biobehavioral Sciences, Stefan and Shirley Hatos Center for Neuropharmacology, Semel Institute, University of California, Los Angeles, CA 90095, USA
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78
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La Porta C, Bura SA, Aracil-Fernández A, Manzanares J, Maldonado R. Role of CB1 and CB2 cannabinoid receptors in the development of joint pain induced by monosodium iodoacetate. Pain 2013. [DOI: 10.1016/j.pain.2012.10.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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79
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Inhibition of Activity of GABA Transporter GAT1 by δ-Opioid Receptor. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:818451. [PMID: 23365600 PMCID: PMC3543822 DOI: 10.1155/2012/818451] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/04/2012] [Accepted: 11/04/2012] [Indexed: 01/16/2023]
Abstract
Analgesia is a well-documented effect of acupuncture. A critical role in pain sensation plays the nervous system, including the GABAergic system and opioid receptor (OR) activation. Here we investigated regulation of GABA transporter GAT1 by δOR in rats and in Xenopus oocytes. Synaptosomes of brain from rats chronically exposed to opiates exhibited reduced GABA uptake, indicating that GABA transport might be regulated by opioid receptors. For further investigation we have expressed GAT1 of mouse brain together with mouse δOR and μOR in Xenopus oocytes. The function of GAT1 was analyzed in terms of Na+-dependent [3H]GABA uptake as well as GAT1-mediated currents. Coexpression of δOR led to reduced number of fully functional GAT1 transporters, reduced substrate translocation, and GAT1-mediated current. Activation of δOR further reduced the rate of GABA uptake as well as GAT1-mediated current. Coexpression of μOR, as well as μOR activation, affected neither the number of transporters, nor rate of GABA uptake, nor GAT1-mediated current. Inhibition of GAT1-mediated current by activation of δOR was confirmed in whole-cell patch-clamp experiments on rat brain slices of periaqueductal gray. We conclude that inhibition of GAT1 function will strengthen the inhibitory action of the GABAergic system and hence may contribute to acupuncture-induced analgesia.
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80
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Chen HJ, Xie WY, Hu F, Zhang Y, Wang J, Wang Y. Disruption of δ-opioid receptor phosphorylation at threonine 161 attenuates morphine tolerance in rats with CFA-induced inflammatory hypersensitivity. Neurosci Bull 2012; 28:182-92. [PMID: 22466129 DOI: 10.1007/s12264-012-1216-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVE Our previous study identified Threonine 161 (Thr-161), located in the second intracellular loop of the δ-opioid receptor (DOR), as the only consensus phosphorylation site for cyclin-dependent kinase 5 (Cdk5). The aim of this study was to assess the function of DOR phosphorylation by Cdk5 in complete Freund's adjuvant (CFA)-induced inflammatory pain and morphine tolerance. METHODS Dorsal root ganglion (DRG) neurons of rats with CFA-induced inflammatory pain were acutely dissociated and the biotinylation method was used to explore the membrane localization of phosphorylated DOR at Thr-161 (pThr-161-DOR), and paw withdrawal latency was measured after intrathecal delivery of drugs or Tat-peptide, using a radiant heat stimulator in rats with CFA-induced inflammatory pain. RESULTS Both the total amount and the surface localization of pThr-161-DOR were significantly enhanced in the ipsilateral DRG following CFA injection. Intrathecal delivery of the engineered Tat fusion-interefering peptide corresponding to the second intracellular loop of DOR (Tat-DOR-2L) increased inflammatory hypersensitivity, and inhibited DOR- but not µ-opioid receptor-mediated spinal analgesia in CFA-treated rats. However, intrathecal delivery of Tat-DOR-2L postponed morphine antinociceptive tolerance in rats with CFA-induced inflammatory pain. CONCLUSION Phosphorylation of DOR at Thr-161 by Cdk5 attenuates hypersensitivity and potentiates morphine tolerance in rats with CFA-induced inflammatory pain, while disruption of the phosphorylation of DOR at Thr-161 attenuates morphine tolerance.
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Affiliation(s)
- Hai-Jing Chen
- Neuroscience Research Institute, Peking University, Department of Neurobiology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
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81
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Harvey JH, Long DH, England PM, Whistler JL. Tuned-Affinity Bivalent Ligands for the Characterization of Opioid Receptor Heteromers. ACS Med Chem Lett 2012; 3:640-644. [PMID: 23585918 DOI: 10.1021/ml300083p] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Opioid receptors, including the mu and delta opioid receptors (MOR and DOR) are important targets for the treatment of pain. Although there is mounting evidence that these receptors form heteromers, the functional role of the MOR/DOR heteromer remains unresolved. We have designed and synthesized bivalent ligands as tools to elucidate the functional role of the MOR/DOR heteromer. Our ligands (L2 and L4) are comprised of a compound with low affinity at the DOR tethered to a compound with high affinity at the MOR, with the goal of producing ligands with "tuned affinity" at MOR/DOR heteromers compared to DOR homomers. Here we show that both L2 and L4 demonstrate enhanced affinity at MOR/DOR heteromers compared to DOR homomers, thereby providing unique pharmacological tools to dissect the role of the MOR/DOR heteromer in pain.
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Affiliation(s)
- Jessica H. Harvey
- Ernest Gallo Clinic and Research Center, 5858 Horton Street, Suite 200,
Emeryville, California 94608, United States
- University of California, San Francisco, Genentech Hall, 600 16th Street, San
Francisco, California 94158, United States
| | - Darcie H. Long
- Ernest Gallo Clinic and Research Center, 5858 Horton Street, Suite 200,
Emeryville, California 94608, United States
| | - Pamela M. England
- University of California, San Francisco, Genentech Hall, 600 16th Street, San
Francisco, California 94158, United States
| | - Jennifer L. Whistler
- Ernest Gallo Clinic and Research Center, 5858 Horton Street, Suite 200,
Emeryville, California 94608, United States
- University of California, San Francisco, Genentech Hall, 600 16th Street, San
Francisco, California 94158, United States
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82
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Opioid glycopeptide analgesics derived from endogenous enkephalins and endorphins. Future Med Chem 2012; 4:205-26. [PMID: 22300099 DOI: 10.4155/fmc.11.195] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Over the past two decades, potent and selective analgesics have been developed from endogenous opioid peptides. Glycosylation provides an important means of modulating interaction with biological membranes, which greatly affects the pharmacodynamics and pharmacokinetics of the resulting glycopeptide analogues. Furthermore, manipulation of the membrane affinity allows penetration of cellular barriers that block efficient drug distribution, including the blood-brain barrier. Extremely potent and selective opiate agonists have been developed from endogenous peptides, some of which show great promise as drug candidates.
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83
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van Rijn RM, Brissett DI, Whistler JL. Distinctive modulation of ethanol place preference by delta opioid receptor-selective agonists. Drug Alcohol Depend 2012; 122:156-9. [PMID: 22018601 PMCID: PMC3279630 DOI: 10.1016/j.drugalcdep.2011.09.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 09/16/2011] [Accepted: 09/22/2011] [Indexed: 10/16/2022]
Abstract
BACKGROUND Naltrexone is one of the few drugs approved by the Federal Drug Administration for the treatment of alcoholism. However, naltrexone is only effective in a subpopulation of treatment-seeking alcohol abusers, and suffers from compliance issues. The non-selective nature of this opioid antagonist likely contributes to its side effects and poor therapeutic efficacy. Drugs selectively targeting delta opioid receptor subtypes offer a potential way to treat alcohol abuse disorders. We have recently shown that delta subtype-selective agonists TAN-67 and SNC80 can have opposing effects on alcohol consumption, while having similar effects on alcohol withdrawal-induced anxiety. METHODS We studied the ability of TAN-67 and SNC80 to induce place preference in naïve and ethanol exposed C57BL/6 mice and determined the effect of these agonists on the expression of ethanol place preference. RESULTS We show that TAN-67 and SNC80 have opposing actions on ethanol place preference. However, neither of the drugs induces place preference by themselves at doses that are therapeutically effective in mice. Interestingly, SNC80, like naltrexone reduces ethanol place preference, however we have previously shown that SNC80 increases ethanol consumption at the tested dose. Similar to naltrexone, TAN-67 reduces alcohol consumption, but we show here that it may be due to an increase in ethanol place preference. Importantly, we found that chronic ethanol exposure does not increase the rewarding properties of the DOR subtype selective agonists. CONCLUSIONS Our results provide a better understanding of how DOR subtype selective drugs could potentially be used for treatment of alcohol abuse disorders.
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Affiliation(s)
- Richard M. van Rijn
- Corresponding author: Ernest Gallo Clinic and Research Center, Dept. of Neurology, University of California, San Francisco, 5858 Horton St., Suite 200, Emeryville, CA 94608. Tel.: 510-985-3131; Fax: 510-985-3101;
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84
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Nielsen CK, Simms JA, Bito-Onon JJ, Li R, Ananthan S, Bartlett SE. The delta opioid receptor antagonist, SoRI-9409, decreases yohimbine stress-induced reinstatement of ethanol-seeking. Addict Biol 2012; 17:224-34. [PMID: 21309957 DOI: 10.1111/j.1369-1600.2010.00295.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A major problem in treating alcohol use disorders (AUDs) is the high rate of relapse due to stress and re-exposure to cues or an environment previously associated with alcohol use. Stressors can induce relapse to alcohol-seeking in humans or reinstatement in rodents. Delta opioid peptide receptors (DOP-Rs) play a role in cue-induced reinstatement of ethanol-seeking; however, their role in stress-induced reinstatement of ethanol-seeking is not known. The objective of this study was to determine the role of DOP-Rs in yohimbine-stress-induced reinstatement of ethanol-seeking. Male, Long-Evans rats were trained to self-administer 10% ethanol in daily 30-minute operant self-administration sessions using a FR3 schedule of reinforcement, followed by extinction training. Once extinction criteria were met, we examined the effects of the DOP-R antagonist, SoRI-9409 (0-5 mg/kg, i.p.) on yohimbine (2 mg/kg, i.p.) stress-induced reinstatement. Additionally, DOP-R-stimulated [(35) S]GTPγS binding was measured in brain membranes and plasma levels of corticosterone (CORT) were determined. Pre-treatment with SoRI-9409 decreased yohimbine stress-induced reinstatement of ethanol-seeking but did not affect yohimbine-induced increases in plasma CORT levels. Additionally, yohimbine increased DOP-R-stimulated (35) [S]GTPγS binding in brain membranes of ethanol-trained rats, an effect that was inhibited by SoRI-9409. This suggests that the DOP-R plays an important role in yohimbine-stress-induced reinstatement of ethanol-seeking behavior, and DOP-R antagonists may be promising candidates for further development as a treatment for AUDs.
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Affiliation(s)
- Carsten K Nielsen
- Ernest Gallo Clinic and Research Center, University of California San Francisco, 5858 Horton Street, Emeryville, CA, USA
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85
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van Rijn RM, Brissett DI, Whistler JL. Emergence of functional spinal delta opioid receptors after chronic ethanol exposure. Biol Psychiatry 2012; 71:232-8. [PMID: 21889123 PMCID: PMC4086708 DOI: 10.1016/j.biopsych.2011.07.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 07/06/2011] [Accepted: 07/07/2011] [Indexed: 11/15/2022]
Abstract
BACKGROUND The delta opioid receptor (DOR) is a promising target to treat multiple indications, including alcoholism, anxiety, and nonmalignant pain. The potential of the DORs has been underappreciated, in part, due to relatively low functional expression of these receptors in naïve states. However, chronic exposure to stress, opioids, and inflammation can induce a redistribution of DORs to the cell surface where they can be activated. Previously, DORs were shown to be selectively/exclusively present in spinal cord circuits mediating mechanical sensitivity but not those mediating thermal nociception under naïve conditions. METHODS We spinally administered DOR and mu opioid receptor (MOR) selective agonists ([D-Pen2,D-Pen5]-Enkephalin, deltorphin II, SNC80, and DAMGO) and antagonists (naltriben and CTAP) and determined thermal antinociception and mechanical sensitivity in wild-type mice or mice with a genetic disruption of DOR or MOR. Thermal antinociception was measured using a radiant heat tail-flick assay; mechanical sensitivity was measured using von Frey filaments. Dose response curves were generated in naïve mice and mice exposed to ethanol in a model of voluntary consumption. RESULTS We show that prolonged exposure to ethanol can promote an upregulation of functional DORs in the spinal cord in thermal pain-mediating circuits but not in those mediating mechanical sensitivity. The upregulated DORs either modulate MOR-mediated analgesia through convergence of circuits or signal transduction pathways and/or interact directly with MORs to form a new functional (heteromeric) unit. CONCLUSIONS Our findings suggest that DORs could be a novel target in conditions in which DORs are redistributed.
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MESH Headings
- Analgesics, Opioid/administration & dosage
- Analgesics, Opioid/pharmacology
- Animals
- Drug Administration Schedule
- Ethanol/administration & dosage
- Ethanol/pharmacology
- Injections, Spinal
- Mice
- Mice, Knockout
- Nociception/drug effects
- Nociception/physiology
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, delta/physiology
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/physiology
- Spinal Cord/drug effects
- Spinal Cord/metabolism
- Up-Regulation/drug effects
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Affiliation(s)
- Richard M van Rijn
- Ernest Gallo Clinic and Research Center, Department of Neurology, University of California San Francisco, Emeryville, California 94608, USA
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86
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Berezowska I, Lemieux C, Chung NN, Ding J, Schiller PW. Novel TIPP (H-Tyr-Tic-Phe-Phe-OH) analogues displaying a wide range of efficacies at the δ opioid receptor. Discovery of two highly potent and selective δ opioid agonists. Bioorg Med Chem Lett 2012; 22:1899-902. [PMID: 22325949 DOI: 10.1016/j.bmcl.2012.01.063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 01/15/2012] [Accepted: 01/17/2012] [Indexed: 10/14/2022]
Abstract
Analogues of the δ opioid antagonist peptide TIPP (H-Tyr-Tic-Phe-Phe-OH; Tic=1,2,3,4-tetrahydroisoquinoline3-carboxylic acid) containing various 4'-[N-(alkyl or aralkyl)carboxamido]phenylalanine analogues in place of Tyr(1) were synthesized. The compounds showed subnanomolar or low nanomolar δ opioid receptor binding affinity and various efficacy at the δ receptor (antagonism, partial agonism, full agonism) in the [(35)S]GTPγS binding assay. Two analogues, [1-Ncp(1)]TIPP (1-Ncp=4'-[N-(2-(naphthalene-1-yl)ethyl)carboxamido]phenylalanine) and [2-Ncp(1)]TIPP (2-Ncp=4'-[N-(2-(naphthalene-2-yl)ethyl)carboxamido]phenylalanine), were identified as potent and selective δ opioid agonists.
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Affiliation(s)
- Irena Berezowska
- Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montreal, 110 Pine Avenue West, Montreal, QC, Canada H2W 1R7
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87
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Delta opioid receptor analgesia: recent contributions from pharmacology and molecular approaches. Behav Pharmacol 2011; 22:405-14. [PMID: 21836459 DOI: 10.1097/fbp.0b013e32834a1f2c] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Delta opioid receptors represent a promising target for the development of novel analgesics. A number of tools have been developed recently that have significantly improved our knowledge of δ receptor function in pain control. These include several novel δ agonists with potent analgesic properties, and genetic mouse models with targeted mutations in the δ opioid receptor gene. Also, recent findings have further documented the regulation of δ receptor function at cellular level, which impacts on the pain-reducing activity of the receptor. These regulatory mechanisms occur at transcriptional and post-translational levels, along agonist-induced receptor activation, signaling and trafficking, or in interaction with other receptors and neuromodulatory systems. All these tools for in-vivo research, and proposed mechanisms at molecular level, have tremendously increased our understanding of δ receptor physiology, and contribute to designing innovative strategies for the treatment of chronic pain and other diseases such as mood disorders.
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88
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Activation of spinal mu- and delta-opioid receptors potently inhibits substance P release induced by peripheral noxious stimuli. J Neurosci 2011; 31:13068-77. [PMID: 21917790 DOI: 10.1523/jneurosci.1817-11.2011] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Over the past few years, δ-opioid receptors (DOPRs) and μ-opioid receptors (MOPRs) have been shown to interact with each other. We have previously seen that expression of MOPR is essential for morphine and inflammation to potentiate the analgesic properties of selective DOPR agonists. In vivo, it is not clear whether MOPRs and DOPRs are expressed in the same neurons. Indeed, it was recently proposed that these receptors are segregated in different populations of nociceptors, with MOPRs and DOPRs expressed by peptidergic and nonpeptidergic fibers, respectively. In the present study, the role and the effects of DOPR- and MOPR-selective agonists in two different pain models were compared. Using preprotachykinin A knock-out mice, we first confirmed that substance P partly mediates intraplantar formalin- and capsaicin-induced pain behaviors. These mice had a significant reduction in pain behavior compared with wild-type mice. We then measured the effects of intrathecal deltorphin II (DOPR agonist) and DAMGO (MOPR agonist) on pain-like behavior, neuronal activation, and substance P release following formalin and capsaicin injection. We found that both agonists were able to decrease formalin- and capsaicin-induced pain, an effect that was correlated with a reduction in the number of c-fos-positive neurons in the superficial laminae of the lumbar spinal cord. Finally, visualization of NK(1) (neurokinin 1) receptor internalization revealed that DOPR and MOPR activation strongly reduced formalin- and capsaicin-induced substance P release via direct action on primary afferent fibers. Together, our results indicate that functional MOPRs and DOPRs are both expressed by peptidergic nociceptors.
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89
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Yoon MH, Kim KS, Lee HG, Kim CM, Kim WM, Choi JI, Kim YO. Synergistic Interaction Between Intrathecal Ginsenosides and Morphine on Formalin-Induced Nociception in Rats. THE JOURNAL OF PAIN 2011; 12:774-81. [DOI: 10.1016/j.jpain.2010.12.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 12/16/2010] [Accepted: 12/31/2010] [Indexed: 12/01/2022]
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90
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Otis V, Sarret P, Gendron L. Spinal activation of delta opioid receptors alleviates cancer-related bone pain. Neuroscience 2011; 183:221-9. [PMID: 21458544 PMCID: PMC3848971 DOI: 10.1016/j.neuroscience.2011.03.052] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 03/21/2011] [Accepted: 03/24/2011] [Indexed: 11/28/2022]
Abstract
Over the past few years, significant progress has been made in cancer therapy. Indeed, the lifespan of cancer patients has significantly increased. Although patients live longer, cancer-related pain remains a daily problem affecting their quality of life, especially when metastases reach the bone. In patients coping with cancer-induced bone pain, morphine and NSAIDs, often used in combination with other medications, are the most commonly used drugs to alleviate pain. However, these drugs have dose-limiting side effects. Morphine and other routinely used opioids are mu opioid receptor (MOPR) agonists. The MOPR is responsible for most opioid-related adverse effects. In the present study, we revealed potent analgesic effects of an intrathecally-administered selective delta opioid receptor (DOPR) agonist, deltorphin II, in a recently developed rat bone cancer model. Indeed, we found that deltorphin II dose-dependently reversed mechanical allodynia 14 days post-surgery in this cancer pain model, which is based on the implantation of mammary MRMT-1 cells in the femur. This effect was DOPR-mediated as it was completely blocked by naltrindole, a selective DOPR antagonist. Using the complete Freund's adjuvant model of inflammatory pain, we further demonstrated that deltorphin II was equipotent at alleviating inflammatory and cancer pain (i.e. similar ED50 values). Altogether, the present results show, for the first time, that activation of spinal DOPRs causes significant analgesia at doses sufficient to reduce inflammatory pain in a rat bone cancer pain model. Our results further suggest that DOPR represents a potential target for the development of novel analgesic therapies to be used in the treatment of cancer-related pain.
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Affiliation(s)
- Valérie Otis
- Département de physiologie et biophysique, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Philippe Sarret
- Département de physiologie et biophysique, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
- Institut de pharmacologie de Sherbrooke, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Louis Gendron
- Département de physiologie et biophysique, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
- Institut de pharmacologie de Sherbrooke, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
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91
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Williams TJ, Akama KT, Knudsen MG, McEwen BS, Milner TA. Ovarian hormones influence corticotropin releasing factor receptor colocalization with delta opioid receptors in CA1 pyramidal cell dendrites. Exp Neurol 2011; 230:186-96. [PMID: 21549703 DOI: 10.1016/j.expneurol.2011.04.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Revised: 03/14/2011] [Accepted: 04/14/2011] [Indexed: 11/19/2022]
Abstract
Stress interacts with addictive processes to increase drug use, drug seeking, and relapse. The hippocampal formation (HF) is an important site at which stress circuits and endogenous opioid systems intersect and likely plays a critical role in the interaction between stress and drug addiction. Our prior studies demonstrate that the stress-related neuropeptide corticotropin-releasing factor (CRF) and the delta-opioid receptor (DOR) colocalize in interneuron populations in the hilus of the dentate gyrus and stratum oriens of CA1 and CA3. While independent ultrastructural studies of DORs and CRF receptors suggest that each receptor is found in CA1 pyramidal cell dendrites and dendritic spines, whether DORs and CRF receptors colocalize in CA1 neuronal profiles has not been investigated. Here, hippocampal sections of adult male and proestrus female Sprague-Dawley rats were processed for dual label pre-embedding immunoelectron microscopy using well-characterized antisera directed against the DOR for immunoperoxidase and against the CRF receptor for immunogold. DOR-immunoreactivity (-ir) was found presynaptically in axons and axon terminals as well as postsynaptically in somata, dendrites and dendritic spines in stratum radiatum of CA1. In contrast, CRF receptor-ir was predominantly found postsynaptically in CA1 somata, dendrites, and dendritic spines. CRF receptor-ir frequently was observed in DOR-labeled dendritic profiles and primarily was found in the cytoplasm rather than at or near the plasma membrane. Quantitative analysis of CRF receptor-ir colocalization with DOR-ir in pyramidal cell dendrites revealed that proestrus females and males show comparable levels of CRF receptor-ir per dendrite and similar cytoplasmic density of CRF receptor-ir. In contrast, proestrus females display an increased number of dual-labeled dendritic profiles and an increased membrane density of CRF receptor-ir in comparison to males. We further examined the functional consequences of CRF receptor-ir colocalization with DOR-ir in the same neuron using the hormone responsive neuronal cell line NG108-15, which endogenously expresses DORs, and assayed intracellular cAMP production in response to CRF receptor and DOR agonists. Results demonstrated that short-term application of DOR agonist SNC80 inhibited CRF-induced cAMP accumulation in NG108-15 cells transfected with the CRF receptor. These studies provide new insights on opioid-stress system interaction in the hippocampus of both males and females and establish potential mechanisms through which DOR activation may influence CRF receptor activity.
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Affiliation(s)
- Tanya J Williams
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA.
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92
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Effect of tooth pulp and periaqueductal central gray stimulation on the expression of genes encoding the selected neuropeptides and opioid receptors in the mesencephalon, hypothalamus and thalamus in rats. Brain Res 2011; 1382:19-28. [DOI: 10.1016/j.brainres.2011.01.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 12/20/2010] [Accepted: 01/09/2011] [Indexed: 11/22/2022]
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93
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Manaheji H. Analgesic effects of methanolic extracts of the leaf or root of Moringa oleifera on complete Freund’s adjuvant-induced arthritis in rats. ACTA ACUST UNITED AC 2011; 9:216-22. [DOI: 10.3736/jcim20110216] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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94
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Ligand-directed trafficking of the δ-opioid receptor in vivo: two paths toward analgesic tolerance. J Neurosci 2011; 30:16459-68. [PMID: 21147985 DOI: 10.1523/jneurosci.3748-10.2010] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
δ-Opioid receptors are G-protein-coupled receptors that regulate nociceptive and emotional responses. It has been well established that distinct agonists acting at the same G-protein-coupled receptor can engage different signaling or regulatory responses. This concept, known as biased agonism, has important biological and therapeutic implications. Ligand-biased responses are well described in cellular models, however, demonstrating the physiological relevance of biased agonism in vivo remains a major challenge. The aim of this study was to investigate the long-term consequences of ligand-biased trafficking of the δ-opioid receptor, at both the cellular and behavioral level. We used δ agonists with similar binding and analgesic properties, but high [SNC80 ((+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide)]- or low [ARM390 (N,N-diethyl-4-(phenyl-piperidin-4-ylidenemethyl)-benzamide)]-internalization potencies. As we found previously, a single SNC80-but not ARM390-administration triggered acute desensitization of the analgesic response in mice. However, daily injections of either compound over 5 d produced full analgesic tolerance. SNC80-tolerant animals showed widespread receptor downregulation, and tolerance to analgesic, locomotor and anxiolytic effects of the agonist. Hence, internalization-dependent tolerance developed, as a result of generalized receptor degradation. In contrast, ARM390-tolerant mice showed intact receptor expression, but δ-opioid receptor coupling to Ca²+ channels was abolished in dorsal root ganglia. Concomitantly, tolerance developed for agonist-induced analgesia, but not locomotor or anxiolytic responses. Therefore, internalization-independent tolerance was produced by anatomically restricted adaptations leading to pain-specific tolerance. Hence, ligand-directed receptor trafficking of the δ-opioid receptor engages distinct adaptive responses, and this study reveals a novel aspect of biased agonism in vivo.
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95
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Dubois D, Gendron L. Delta opioid receptor-mediated analgesia is not altered in preprotachykinin A knockout mice. Eur J Neurosci 2010; 32:1921-9. [DOI: 10.1111/j.1460-9568.2010.07466.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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96
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Dissociation of μ- and δ-opioid inhibition of glutamatergic synaptic transmission in superficial dorsal horn. Mol Pain 2010; 6:71. [PMID: 20977770 PMCID: PMC2987996 DOI: 10.1186/1744-8069-6-71] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 10/26/2010] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND There is anatomical and behavioural evidence that μ- and δ-opioid receptors modulate distinct nociceptive modalities within the superficial dorsal horn. The aim of the present study was to examine whether μ- and δ-opioid receptor activation differentially modulates TRP sensitive inputs to neurons within the superficial dorsal horn. To do this, whole cell patch clamp recordings were made from lamina I - II neurons in rat spinal cord slices in vitro to examine the effect of opioids on TRP agonist-enhanced glutamatergic spontaneous miniature excitatory postsynaptic currents (EPSCs). RESULTS Under basal conditions the μ-opioid agonist DAMGO (3 μM) reduced the rate of miniature EPSCs in 68% of neurons, while the δ- and κ-opioid agonists deltorphin-II (300 nM) and U69593 (300 nM) did so in 13 - 17% of neurons tested. The TRP agonists menthol (400 μM) and icilin (100 μM) both produced a Ca2+-dependent increase in miniature EPSC rate which was unaffected by the voltage dependent calcium channel (VDCC) blocker Cd2+. The proportion of neurons in which deltorphin-II reduced the miniature EPSC rate was enhanced in the presence of icilin (83%), but not menthol (0%). By contrast, the proportion of DAMGO and U69593 responders was unaltered in the presence of menthol (57%, 0%), or icilin (57%, 17%). CONCLUSIONS These findings demonstrate that δ-opioid receptor activation selectively inhibits inputs activated by icilin, whereas μ-opioid receptor activation has a more widespread effect on synaptic inputs to neurons in the superficial dorsal horn. These findings suggest that δ-opioids may provide a novel analgesic approach for specific, TRPA1-like mediated pain modalities.
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97
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van Rijn RM, Brissett DI, Whistler JL. Dual efficacy of delta opioid receptor-selective ligands for ethanol drinking and anxiety. J Pharmacol Exp Ther 2010; 335:133-9. [PMID: 20605909 DOI: 10.1124/jpet.110.170969] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Alcoholism and anxiety disorders have a huge impact on society and afflict 17.6 million and 40 million people in the United States, respectively. A strong comorbidity exists between alcoholism and anxiety disorders. Indeed, alcohol withdrawal-induced anxiety is a primary contributing factor for relapse, and anxiolytics are a common adjuvant therapy prescribed for treatment-seeking alcoholics. It is thought that the use of alcohol to self-medicate and relieve anxiety contributes to the development of addiction. Treatment for anxiety disorders and alcoholism exist but are not universally effective. The delta opioid receptor (DOR) plays a role in both alcohol consumption and anxiety, making it a very interesting clinical target. Two pharmacologically distinct DORs have been described: DOR1 and DOR2. We find here that the relative specificity of DOR agonists for DOR1 or DOR2 can greatly affect the effects they exert on ethanol consumption and anxiety. The DOR1 agonist 2-methyl-4aα-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12aα-octahydro-quinolino[2,3,30g]isoquinoline (TAN-67), although not effective in decreasing anxiety-like behavior in naive mice, has anxiolytic-like properties in ethanol-withdrawn mice. In contrast, a less subtype-selective agonist, (+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80), while also reducing anxiety-like behavior, increases ethanol consumption. In addition, we found that the conical anxiolytic diazepam [DZ; 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2(1H)-one] is a less effective anxiolytic in ethanol-withdrawn mice than in naive mice. Together, our findings suggest that selective DOR agonists can decrease anxiety-like behavior and are more effective than diazepam at reducing ethanol consumption. We believe the dual efficacy of DOR1 agonists makes these receptors an interesting therapeutic target for treatment-seeking alcoholics.
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Affiliation(s)
- Richard M van Rijn
- Ernest Gallo Clinic and Research Center, Department of Neurology, University of California San Francisco, Emeryville, CA 94608, USA
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98
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Insights into subtype selectivity of opioid agonists by ligand-based and structure-based methods. J Mol Model 2010; 17:477-93. [DOI: 10.1007/s00894-010-0745-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Accepted: 05/04/2010] [Indexed: 11/24/2022]
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99
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Codd EE, Ma J, Zhang SP, Stone DJ, Colburn RW, Brandt MR, Chevalier KM, Zhu Y, Peng S, Cai C, Acton PD, Flores CM. Ex vivo delta opioid receptor autoradiography: CNS receptor occupancy of two novel compounds over their antihyperalgesic dose range. Pharmacol Biochem Behav 2010; 96:130-5. [PMID: 20438745 DOI: 10.1016/j.pbb.2010.04.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 04/14/2010] [Accepted: 04/23/2010] [Indexed: 11/19/2022]
Abstract
Discovered as part of an effort to identify delta opioid (DOPr or DOR) agonist analgesics, JNJ-20788560 and JNJ-39204880 exhibited high DOR affinity, with K(i) values of 1.7 and 2.0nM, respectively, and were selective for DOR over the mu opioid receptor (MOPr or MOR), with 596- and 122-fold selectivity, respectively. Both compounds stimulated DOR but not MOR induced GTPgammaS binding and were effective antihyperalgesic agents in the complete Freund's adjuvant model of thermal hyperalgesia in the rat, with oral ED(50) values of 13.5 and 35mg/kg, corresponding to plasma levels of 1 and 9microM, respectively. Autoradiographic analysis of DOR and MOR occupancy in sections of brain (striatum) and lumbar spinal cord (L4-L6) was determined ex vivo, using radiolabeled naltrindole or DAMGO. Quantitative image analysis resulted in striatal DOR ED(50) values of 6.9 and 10.7mg/kg, for JNJ-20788560 and JNJ-39204880 respectively, and spinal cord values of 6.4 and 3.2mg/kg, respectively. Neither compound dose-dependently occupied MOR within the dose range studied. Thus, this study confirmed the DOR selectively over MOR of both compounds following their oral administration, and further demonstrated dose-dependent DOR occupancy by each compound across its antihyperalgesic dose range. Importantly, these in vitro, in vivo, and ex vivo data revealed that the greater in vitro potency of JNJ-20788560 was paralleled by its greater in vivo potency, although JNJ-39204880 achieved higher plasma levels following its oral administration. The receptor occupancy levels observed at the pharmacologic ED(50) doses of these compounds suggest the need for greater target engagement by JNJ-39204880 than by JNJ-20788560 to elicit a similar therapeutic response.
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MESH Headings
- Analgesics, Opioid/blood
- Analgesics, Opioid/pharmacology
- Animals
- Autoradiography/methods
- Azabicyclo Compounds/blood
- Azabicyclo Compounds/pharmacology
- Corpus Striatum/diagnostic imaging
- Corpus Striatum/metabolism
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/analysis
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Lumbar Vertebrae/diagnostic imaging
- Male
- Naltrexone/analogs & derivatives
- Naltrexone/analysis
- Pain Measurement/drug effects
- Pyrimidines/blood
- Pyrimidines/pharmacology
- Pyrrolidines/blood
- Pyrrolidines/pharmacology
- Radiography
- Radioligand Assay/methods
- Rats
- Rats, Sprague-Dawley
- Rats, Wistar
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Spinal Cord/diagnostic imaging
- Spinal Cord/metabolism
- Xanthenes/blood
- Xanthenes/pharmacology
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Affiliation(s)
- Ellen E Codd
- Drug Discovery, Johnson & Johnson Pharmaceutical Research and Development, LLC, Spring House, PA 19477, USA.
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100
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Abstract
Similar to mu opioid receptors, kappa and delta opioid receptors reside in the periphery, the dorsal root ganglion, the spinal cord, and in supraspinal regions associated with pain modulation. Both delta and kappa opioid agonists have been shown to activate pain inhibitory pathways in the central nervous system. Yet, currently there are only a few pharmacologic agents that target kappa receptors, and none that target delta receptors. Spurred by the need for an efficacious analgesic without the unwanted side effects associated with the typical clinical profile of mu opioid agonists, new research has provided insight into why the development of effective kappa and delta opioid receptor agonists has remained elusive thus far, and importantly, how these obstacles may be overcome. For example, for delta opioid agonists to be effective, a state of inflammation may be required as this induces delta opioid receptors to migrate to the surface of neuronal cells and thereby become accessible to delta opioid agonists. Studies have shown that delta opioid agonists can provide relief of inflammatory pain and malignant bone pain. Meanwhile, peripherally restricted kappa opioid agonists have been developed to target kappa opioid receptors located on visceral and somatic afferent nerves for relief of inflammatory, visceral, and neuropathic chronic pain. The recently shown efficacy of these analgesics combined with a possible lower abuse potential and side effect burden than mu opioid receptor agonists makes delta and peripherally restricted kappa opioid receptor agonists promising targets for treating pain.
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